Maraging steel

Abstract

The present invention relates to a maraging steel containing, in terms of mass %, 0.10≤C≤0.35, 9.0≤Co≤20.0, 1.0≤(Mo+W/2)≤2.0, 1.0≤Cr≤4.0, a certain amount of Ni, a certain amount of Al, and V+Nb≤0.60, with the balance being Fe and inevitable impurities, in which in a case of V+Nb≤0.020, the amount of Ni is 6.0≤Ni≤9.4 and the amount of Al is 1.4≤Al≤2.0, and in a case of 0.020<V+Nb≤0.60, the amount of Ni is 6.0≤Ni≤20.0 and the amount of Al is 0.50≤Al≤2.0.

What is claimed is: 
     
       1. A maraging steel consisting of:
 as essential components,
 0.10 mass %≤C≤0.35 mass %, 
 9.0 mass %≤Co≤20.0 mass %, 
 1.0 mass %≤(Mo+W/2)≤2.0 mass %, 
 1.0 mass %≤Cr≤2.6 mass %, 
 6.0 mass %≤Ni≤20.0 mass %, 
 0.50 mass %≤Al≤2.0 mass %, and 
 0.020 mass %<V+Nb≤0.60 mass %, and 
 
 as optional components,
 Ti≤0.10 mass %, 
 S≤0.0010 mass %, 
 N≤0,0020 mass %, 
 B≤0.0050 mass %, and 
 Si≤1.0 mass %, 
 
 with a balance being Fe and inevitable impurities, 
 wherein a number of AlN inclusion having a minor axe of 1.0 μm or smaller and an aspect ratio of 10 or larger is 0 per 100 mm 2  when observed under Scanning Electron Microscope (SEM), and 
 wherein a following relational expression is satisfied:
   Parameter X≥13.2,
 
 
 wherein X=5.5[C]+11.6[Si]−1.4[Ni]−5[Cr]−1.2[Mo]+0.7[Co]+41.9[Al]−7[V]−98.4[Nb]+3.3[B], and 
 each element symbol with braces represents a content (by mass %) of each element. 
 
     
     
       2. The maraging steel according to  claim 1 , wherein a content of V satisfies:
 0.050 mass %≤V≤0.60 mass %. 
 
     
     
       3. The maraging steel according to  claim 1 , wherein a content of Nb satisfies:
 0.050 mass %≤Nb≤0.60 mass %. 
 
     
     
       4. The maraging steel according to  claim 1 , having a tensile strength of at least 2,300 MPa at (23° C.). 
     
     
       5. The maraging steel according to  claim 1 , having an elongation of at least 8% at (23° C.). 
     
     
       6. The maraging steel according to  claim 1 , wherein a content of B satisfies:
 0.0010 mass %≤B≤0.0050 mass %. 
 
     
     
       7. The maraging steel according to  claim 1 , wherein a content of Si satisfies:
 0.10 mass %≤Si≤1.0 mass %. 
 
     
     
       8. The maraging steel according to  claim 1 , used as an engine shaft of an aircraft. 
     
     
       9. The maraging steel according to  claim 1 , wherein the essential components include Mo and W. 
     
     
       10. The maraging steel according to  claim 9 , wherein 1.0 mass %≤(Mo+W/2)≤1.6 mass %. 
     
     
       11. The maraging steel according to  claim 1 , wherein 1.0 mass %≤(Mo+W/2)≤1.6 mass %. 
     
     
       12. The maraging steel according to  claim 1 , wherein an amount of Ni is:
 6.0 mass %≤Ni≤9.0 mass %. 
 
     
     
       13. A maraging steel consisting of:
 as essential components,
 0.10 mass %≤C≤0.35 mass %, 
 9.0 mass %≤Co≤20.0 mass %, 
 1.0 mass %≤(Mo+W/2)≤2.0 mass %, 
 1.0 mass %≤Cr≤2.6 mass %, 
 6.0 mass %≤Ni≤9.4 mass %, and 
 1.45 mass %≤Al≤2.0 mass %, and 
 
 as optional components,
 Ti≤0.10 mass %, 
 S≤0.0010 mass %, 
 N≤0.0020 mass %, 
 V+Nb≤0.020 mass %, 
 B≤0.0050 mass %, and 
 Si≤1.0 mass %, 
 
 with a balance being Fe and inevitable impurities, 
 wherein a number of AlN inclusion having a minor axe of 1.0 μm or smaller and an aspect ratio of 10 or larger is 2 or less per 100 mm 2  when observed under Scanning Electron Microscope (SEM). 
 
     
     
       14. The maraging steel according to  claim 13 , wherein a following relational expression is satisfied:
   Parameter X≥45,
 
 wherein X=5.5[C]+11.6[Si]−1.4[Ni]−5[Cr]−1.2[Mo]+0.7[Co]+41.9[Al]−7[V]−98.4[Nb]+3.3[B], and 
 each element symbol with braces represents a content (by mass %) of each element. 
 
     
     
       15. The maraging steel according to  claim 13 , having a tensile strength of at least 2,300 MPa at (23° C.). 
     
     
       16. The maraging steel according to  claim 13 , having an elongation of at least 8% at (23° C.). 
     
     
       17. The maraging steel according to  claim 13 , wherein a content of B satisfies:
 0.0010 mass %≤B≤0.0050 mass %. 
 
     
     
       18. The maraging steel according to  claim 13 , wherein a content of Si satisfies:
 0.10 mass %≤Si≤1.0 mass %. 
 
     
     
       19. The maraging steel according to  claim 13 , used as an engine shaft of an aircraft. 
     
     
       20. The maraging steel according to  claim 13 , wherein
 1.0 mass %≤(Mo+W/2)≤1.6 mass %.